JPH0127638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording and reproducing device for PAL and SECAM color television signals, which enables long-time recording, reduces adjacent signal interference of color signals, and supports static playback, slow motion playback, and high-speed playback. The structure is such that normal color reproduction can be performed during special reproduction such as reproduction and reverse reproduction as well as during normal reproduction.

In recent years, there has been a trend toward higher density in home VCRs.
In a two-head helical scan VTR, a recording method in which the two heads are provided with an azimuth angle and no guard band is provided between adjacent tracks is becoming common.

Figure 1 shows the VHS system for PAL and SECAM signals.
Shows the recording pattern of a VTR. In Fig. 1, -A, -B, -A, -B... represent recording tracks, -A--A, -A... are trajectories written by head A, -B, -B, -B …
... is a locus drawn by the B head, and there is an azimuth angle of ±6° between the A head and the B head (not shown in the figure).

Further, -1, -2, -3, . . . represent line numbers, and the appended R and B represent the color signals of the lines. In other words, in the PAL signal, the phase of the RY signal is inverted for each line, but
A positive state of the RY signal is represented by R, and a negative state is represented by B. In addition, in the SECAM signal, R-
Although the Y signal and BY signal are transmitted alternately,
The state in which the RY signal is transmitted is represented by R, and the state in which the BY signal is transmitted is represented by B. Also,
αH is the amount by which the start ends of adjacent tracks deviate in the direction of track extension, expressed in units of one horizontal scanning period.
For VTRs, αH is set to 1.5. Note that the track pitch T _p at this time was 49 μm, and the tape speed was 23.4 mm/S.

In this way, for VHS system PAL, SECAM signal
In a VTR, horizontal synchronization signals between adjacent tracks are lined up, and adjacent color signals are also lined up. That is, the neighbor of R is R, and the neighbor of B is B.

Next, the case of performing special playback (still, slow, high-speed playback, and reverse playback) with such a VTR will be explained. Figure 2 shows the trajectory of the head for static playback, Figure 3 for high-speed playback, and Figure 4 for reverse playback. Figure 5 shows the trajectory of the head for static playback, Figure 6 for high-speed playback, and Figure 7 for reverse playback. The position of the horizontal synchronization signal and the order of the color signals in the video signal in each case of playback,
Furthermore, a reproduced signal diagram showing changes in the envelope waveform is shown.

A is the playback trajectory of the A head, and B is the playback trajectory of the B head. However, in Fig. 2, both heads A and B draw the same trajectory. As mentioned above, since both heads A and B are provided with an azimuth angle, head A receives only the signal of the trajectory written by head A, and
The head reproduces only the signal of the trajectory written by the B head. Therefore, in FIGS. 2 to 4, the signals in the shaded areas are reproduced. In FIG. 2, the A head reproduces the signal indicated by the diagonal line A, and the B head reproduces the signal indicated by the diagonal line B. During such special playback, the recording trajectory may be jumped during one playback of one head, or the signal order may be different from that in normal playback when switching heads. These states can be categorized as follows: 1. During one playback of one head, a transition occurs to the next recording trajectory (during high-speed playback).

[In Figure 3, from the A trajectory of the A head]
Transition to A trajectory, and B head transition from -B trajectory to -B trajectory] 2. Transition to the next recording trajectory when switching heads (during stationary, slow, high speed, and reverse playback).

[In Figure 2, the transition from the -B trajectory of the B head to the -A trajectory of the A head, and the transition from the -A trajectory of the A head to the -B trajectory in Figure 4] 3 Recording three positions ahead when switching heads Move to trajectory (during high-speed playback).

[Transition from the -A trajectory of the A head to the -B trajectory of the B head in Figure 3] 4. Transition to the previous trajectory when switching heads (during stationary, slow, and reverse playback).

[In Figure 2, the transition from the -A trajectory of head A to the -B trajectory of head B, and in Figure 4, the transition from the -B trajectory of head B to the -A trajectory of head A] 5 1 of one head During playback, move to the previous recording trajectory (when playing still, slow, or in reverse).

[In Figure 4, from the -A trajectory of the A head -A
There are five ways: transition to trajectory, transition from -A trajectory to -A trajectory, and transition from -B trajectory to -B trajectory of the B head. In the five cases described above, the continuity of the horizontal synchronization signal and the continuity of the color signal are important. If the continuity of the horizontal synchronization signal is lost, skew distortion will occur on the screen. Next, we will discuss the continuity of color signals. In PAL and SECAM signals, the color signal is switched for each line.
That is, in PAL, the phase of the carrier wave of the R-Y signal is inverted for each line, and in SECAM, the phase of the carrier wave of the R-Y signal is inverted for each line.
The Y signal and BY signal are switched and transmitted line by line. Therefore, if the order of the color signals is reversed in the middle of the field or for the first time, the color discrimination circuit of the television receiver may malfunction, or it may take a long time to draw in the color, resulting in no color being displayed, or in the middle of the screen or in the middle of the screen. The hue may be distorted at the top.

Looking at the five cases mentioned above on a VTR with the recording pattern shown in Figure 1, 1). and 5). In this case, since the horizontal synchronization signal and the color signal are lined up in the recording pattern, both the continuity of the horizontal synchronization signal and the continuity of the color signal are maintained. 2). In this case, the switching of the heads is carried out in exactly the same way as in the case of normal reproduction, so that the continuity of the horizontal synchronizing signal and color signal is maintained. 3).
In this case, the signal reproduced when switching heads is skipped over 2 tracks and 2αH lines. As can be seen in Figs. 3 and 6, in the transition from -A to -B, -B track, -A track and,
-312 line, -313 line (1/2 line) of -A track, -313 line (1/2 line), -314 line of -B track are skipped,
- Transition from line 311 to line 315. Therefore, the total number of lines skipped is 625 + 2αH = 628
(αH=1.5), which is an even number, so the continuity of the horizontal synchronization signal and color signal is maintained.
4). In this case, when switching heads, the reproduced signal returns to the previous track and returns to the 2αH line.

As can be seen in Figures 2 and 5, in the transition from -A to -B, there is a transition from -314 line of the A track to -312 line of the -B track. In other words, go back 625+2αH=628 lines. As can be seen in Figures 4 and 7, when moving from -B track to -A track, 625 +
Go back 2αH=628 lines. Since this is an even number, the continuity of the horizontal synchronization signal and color signal is maintained.

In this way, the recording pattern shown in Figure 1
In a VTR, the continuity of the horizontal synchronization signal and color signal is always maintained even during special playback.

Next, for VHS system PAL, SECAM signal or VTR
A basic block diagram of the signal processing is shown in FIG. 8 and will be briefly explained. In Fig. 8, 1 is a video signal input terminal, 3 is a low-pass filter, 3 is a band filter,
4 is a frequency modulator, 5 is a frequency converter, 6 is an adder, 7 is a head, 8 is a high-pass filter, 9 is a low-pass filter, 10 is a frequency demodulator, 11 is a frequency converter, 12 is an adder, 13 is a video signal output terminal. A video signal applied to an input terminal 1 is separated into a luminance signal and a carrier color signal by a low-pass filter 2 and a bandpass filter 3. The luminance signal is converted into a frequency modulated wave by a frequency modulator 4 and guided to an adder 6.
On the other hand, the carrier color signal is converted to a lower frequency by a frequency converter 5, superimposed on the frequency modulated wave by an adder 6, and recorded on a tape via a head 7. During this frequency conversion to the low frequency range, signal processing is applied to each of the PAL and SECAM signals. The signal reproduced from the head 7 is separated by a high pass filter 8 and a low pass filter 9 into a frequency modulated wave of a luminance signal and a carrier color signal converted to a low pass. The frequency modulated wave is guided to a frequency demodulator 10 and demodulated to obtain a reproduced luminance signal, and an adder 1
Leads to 2. On the other hand, the frequency converter 11 converts the low-frequency carrier color signal back to its original frequency, and the adder 12 adds it to the reproduced luminance signal, so that a reproduced video signal is obtained at the output terminal 13. In the process of returning the carrier color signal to its original frequency in the frequency converter 11, signal processing is applied to each of the PAL and SECAM signals.

The present invention provides a method for obtaining continuity of horizontal synchronization signals and color signals during special playback by increasing the density even further than the pattern shown in FIG. 1, or by using a different pattern. .

As explained in FIGS. 2 to 4, there are five cases in which signal discontinuity may occur during special playback. αH in any pattern for each case
This section explains the continuity of horizontal synchronization signals and color signals. 1). In case of 625+ when transferring track
Move to the 2αH line. 5). 625+ for
Move to the front of the 2αH line. Also, as mentioned above, 2) when switching heads. In this case, the signal transitions in exactly the same way as during normal playback, and the continuity of the horizontal sync signal and color signal is maintained in any pattern.
3). In this case, move to the 625+2αH line, 4).
In this case, move to the front of the 625+2αH line. Therefore,
The condition for the horizontal synchronization signal to always be continuous in these cases is that the number of skipped lines or the number of lines reversed is an integer, that is,
625+2αH is an integer, so αH=n/2 (n: integer). Further, the condition for the color signal to be continuous is that 625+2αH is an even number, that is, 2αH is an odd number, and αH=(2n+1)/2 (n: integer).

In view of the above points, the present invention attempts to obtain continuity of color signals even during special reproduction when the recording density is further increased than the pattern shown in FIG. 1 or when a different pattern is used. . The only pattern with a higher density than that shown in FIG. 1 that satisfies the above-mentioned horizontal synchronization signal and color signal continuity conditions is αH=0.5. However, if αH = 0.5, the tape speed would be 7.8 mm/, the track pitch would be T _p = 16 μm, and the audio performance and image quality would be extremely poor. Therefore, the present invention provides a method for obtaining continuity of color signals during special playback when αH = 1.0 (tape speed 15.6 mm/S, track pitch T _p = 32 μm). With this pattern, both sound and picture quality are almost satisfactory for home use. Note that the present invention is applicable not only to αH=1.0 but also to any pattern of αH=m (m: integer).

FIG. 9 shows the recording pattern when αH=1.0. In FIG. 9, the symbols for track, line and color signals have the same meanings as in FIG. In addition, Fig. 10 shows the trajectory of the head during static playback in this pattern, Fig. 11 shows the trajectory of the head during high-speed playback, and Fig. 12 shows the trajectory of the head during reverse playback.
FIG. 15 shows reproduction signal diagrams showing the horizontal synchronizing signal position, the order of color signals in the video signal, and changes in envelope waveforms for high-speed reproduction and FIG. 15 for reverse reproduction. This corresponds to FIGS. 2 to 4 and 5 to 7 for αH=1.5, and the symbols have the same meanings. When αH is an integer, as can be seen from the above explanation and the reproduction signal diagram, continuity of the horizontal synchronization signal can always be obtained during special reproduction, but the above-mentioned 2) of special reproduction. In any other case, the continuity of the color signal will be disrupted. For these special playback cases,
This will be explained using FIGS. 10 to 15. A is A
B is the reproduction trajectory of the head B, and since the two heads are provided with an azimuth angle as described above, the A head reproduces only the signal of the trajectory recorded by the A head, The B head reproduces only the signal of the trajectory recorded by the B head. Special playback 1). This case corresponds to, for example, when the A head moves from the shaded area -A track to -A track during high-speed reproduction as shown in FIG. 11, and when the B head moves from -B track to -B track. At this time, A recording truck comrades and B
On the recording tracks, the horizontal synchronizing signals are aligned, but the chrominance signals are not aligned, so that a discontinuous portion of the chrominance signal occurs at the transition point ○a of the A head and the transition point ○b of the B head shown in FIG. 3). In the same case as above, during high-speed reproduction as shown in FIGS. 11 and 14, the color signal is changed at the head switching point (switching point ○C shown in FIG. Causes discontinuity. Also, at this time, 1/2 of the -312 lines, all of the -313 lines, and 1/2 of the -314 lines are skipped, and the total number of skipped lines is 625 + 2 = 627, which is an odd number, and because of the color signal continuity mentioned above, It can also be seen that the condition that 625+2αH is an even number is not satisfied. 4). In this case, during static playback as shown in Figs. 10 and 13, the A head - the B head one track before the A track -
This corresponds to the head switching point to the B track, and a discontinuous portion of the color signal occurs. At this time, 1/2 of the 313 line and 1/2 of the 314 line due to A head regeneration,
Furthermore, by reproducing the B head - 1/2 of the 312 line,
- 1/2 of the 313 lines is increased, that is, the total number of lines returned to the previous one is 625 + 2 = 627, which is an odd number, which means that it does not satisfy the above-mentioned condition for color signal continuity that 625 + 2αH is an even number. . Furthermore, during reverse playback shown in FIGS. 12 and 15, discontinuity of the color signal also occurs at the head switching point ○ho from the -B track of the B head to the -A track of the previous A head. Increased by 1 line due to head regeneration and 625 lines due to A head regeneration,
That is, all the lines returned to the previous line are 625+2=627, which is an odd number and does not satisfy the color signal continuity condition as described above.
5). In this case, when performing reverse playback as shown in FIGS. 12 and 5, from the A track of the A head to the A
This corresponds to the point ○ where the head shifts to the track, causing color signal discontinuity in the same way as explained in 1 above, and also corresponds to the point ○ where the B head shifts from the -B track to the -B track. Similarly, color signal discontinuity will occur. As mentioned above, if a discontinuous part occurs, it will cause color disappearance on the TV screen or color variation due to hue disturbance, so if you try to correct this discontinuity to make a continuous color signal, If the order of the color signals after the point where the continuous points occur is reversed, the order of the color signals will have continuity and the above phenomenon will not occur. Looking at FIGS. 13 to 15, it can be seen that the parts where the color signal order is different all correspond to the minimum point of the envelope waveform, that is, the part where the carrier of the head amplifier output disappears. Therefore, the present invention utilizes this phenomenon to align the order of color signals and create stable and continuous color signals.

One embodiment of the present invention is shown in block diagrams in FIGS. 16 and 17. Since each part 1 to 13 is completely the same as the conventional example, the names and operations will be omitted. 16th
Figure 14 shows the 1H delay line, 15 shows the amplifier, 1
6 is an envelope detector, 17 is a pulse generator,
18 is an integrating circuit, 19 is an inhibition circuit, 20 is a flip-flop, 21 is a changeover switch, and 22 is a reproduction mode detection signal input terminal.

The operation of the circuit will be explained using the form shown in FIG. 18. During reproduction, the reproduced luminance signal taken out from the frequency demodulator 10 is applied to the adder 12. On the other hand, a portion of the carrier color signal restored to its original frequency by the frequency converter 11 is applied to the changeover switch 21 as is. On the other hand, part of the carrier color signal is
After passing through the 1H delay line 14, the signal is amplified to a predetermined level by an amplifier 15 and then applied to the changeover switch 21. Although not shown, a part of the reproduced carrier signal obtained from the head amplifier (the signal shown in FIG. 18, 24) is sent to the envelope detector 1.
6 and is detected to obtain a waveform 25, which is then added to the pulse generator 17, and a pulse is generated only at the minimum point of the envelope, that is, the part where the reproduced carrier signal is missing. A waveform 26 is obtained as a detection signal corresponding to the point in time. This waveform 26 is further applied to an integrating circuit 18 to obtain a signal such as waveform 27. Although not shown in the diagram, during actual playback, the signal does not disappear at just one point in the minimum part of the envelope, but before and after that, for a period of several H to + several H, noise and other transients occur when switching heads. The envelope detector detects these as well and generates many small pulses before and after the target pulse output 31, which is not desirable, so it is converted into one stable pulse through the integrating circuit 18 and sent to the subsequent stage. This prevents malfunctions. The resulting pulse 27 is passed through an inhibit circuit 19 and then applied to a flip-flop 20. This is integrator 18
When waveform 27 is applied directly to the flip-flop, the signal 32 produced in waveform 27 by dropouts or other disturbances (shown as 30 in waveform 24)
This is to prevent the flip-flop from malfunctioning and generating an incorrect control signal due to the influence of the signal 3.
2 is prohibited from being input to the flip-flop. This can be obtained by choosing the monomulti rise time constant to an appropriate value related to the envelope fall period. A signal 29 obtained by the flip-flop 20 is taken out as a control signal and applied to a changeover switch 21 to alternately switch between the non-delayed main reproduction carrier color signal and the carrier color signal delayed by one horizontal scanning period. After giving continuity to the color signal order in this way, the adder 12
In addition to this, the signal is superimposed on the reproduced luminance signal and taken out from the output terminal 13 as a reproduced video signal. The above explanation is for the special playback of static, slow, double speed, and reverse playback, but during normal playback, the operation of the flip-flop is stopped by the detection signal input to the playback mode detection signal input terminal 22, and the control signal is is not generated, and the changeover switch always transmits only either the main reproduction carrier color signal which is not delayed or the carrier color signal which is delayed by one horizontal scanning period. Also, in FIG. 17, a dropout compensation circuit 23 is used instead of the envelope detector 16 and pulse generator 17 in FIG.
In this method, pulses corresponding to different parts of the color signal order of the dropout detection signal for detecting the dropout period in the compensation circuit 23 are added to the integrating circuit 18 to compensate for the color signal order in the same manner as described above. The peripheral circuit is the same as that shown in FIG.

Next, the control signal from the flip-flop, the actual color signal, and how they are normally continuous will be explained with reference to FIG. This figure shows the case of high-speed reproduction shown in FIG. 14 as an example.

Note that the same explanation can be given for other special playback modes. 34 shows the envelope change of the reproduced carrier, and in the portion where the color signal order is different, that is, the drop portion of the envelope waveform, the flip-flop output control signal shown in 35 is obtained as described above. 36 shows the color signal order of the main reproduction carrier color signal that is not delayed, 37 shows the color signal order of the carrier color signal delayed by 1H, and 38 shows the carrier color signal output 1 with the color signal order corrected. To explain the carrier color signal output 1 of 38, first, the main signal is used up to the first discontinuous point ○, the delayed signal is used up to the second discontinuous point ○, and the third
It is assumed that the main signal is switched to the main signal up to the discontinuous point ○nu, the delayed signal is switched to the fourth discontinuous point ○, and the main signal period is switched alternately thereafter. The overall flow of the color signal order is that each line is R, B, R, B, R, B... and the odd or even number is always either R or B. The color signal order is continuous. Since this is a condition for
If it is assumed that Therefore, the hue will not be normal on the TV side, but it is only for the period of 2 lines and there is no problem visually. Next, in the line including the second discontinuous point ○, both are B, and there is no problem with the order of the color signals of the lines before and after it. Next, let the line containing the third discontinuous point ○nu be R, and the line containing ○nu' be B.
If it is considered that the first discontinuous point is included, the condition is satisfied, and the hue of only two lines becomes abnormal, so there is no problem. Next, on the line that includes the fourth discontinuous point ○, both become B,
There is no problem with the order of the color signals before and after that.

As described above, although some lines have abnormal hues, overall the color signal order is continuous. Carrier color signal output 2 shown in 39 shows the case where the relationship between the control signal and switching is reversed to that in 38, and up to the first discontinuity point ○, the delayed signal, the second
Main signal up to the discontinuity point ○ri, delayed signal up to the third discontinuity point ○nu, main signal up to the fourth discontinuity point ○ru,
After that, assuming that the signal is switched alternately with the delayed signal, during the period including the first discontinuous point ○
Therefore, there is no problem with the order of the color signals before and after that. Next, if we assume that the line containing the second discontinuous point ○ri is assumed to be R, and the line that includes ○li' is assumed to be B, the result will be the same as in the case of output signal 1, with only two lines abnormal and no other problems. It won't happen. Next, in the line including the third discontinuous point ◯/nu, both become B, and there is no problem with the order of the color signals before and after that.

Next, suppose the line containing the fourth discontinuous point ○ is R,
If the line containing ○ru' is assumed to be B, then 2 as above.
There are no other problems other than the abnormality in the line. Even if the control signal output is reversed or the changeover switch is operated in the opposite direction for some reason, the 3
Since the carrier color signal output 2 of No. 9 is corrected in the same way as the carrier color signal output 1 of No. 38, it does not matter whether the color signal starts from the main signal or the delayed signal. Although the explanation has been given using a high-speed case as an example, correction is performed in both the playback mode of static playback shown in Fig. 10 and reverse playback shown in Fig. 12. Color signals can be extracted.

In the above embodiment, the main signal is taken out as is, and the delayed signal is delayed by one horizontal scanning period. However, even if the fixed period of the carrier color signal is delayed by an even multiple of one horizontal scanning period, the color signal arrangement will be different. Since there is no change in the order, the correction can be made in exactly the same way even if the delayed signal side is further delayed by an even multiple of one horizontal scanning period.

Also, the same effect can be obtained by delaying both carrier color signals and making the delay time difference an odd multiple of one horizontal scanning period.For example, if the main signal side is delayed by one horizontal scanning period, The signal side can also be configured to be delayed by two horizontal scanning periods,
Conversely, the same effect can be achieved even if the main signal side is delayed by two horizontal scanning periods and the signal side is delayed by one horizontal scanning period.

If there is a time difference of an odd multiple of one horizontal scanning period between the two carrier color signals switched in this manner, carrier color signals having a continuous color signal order can be obtained.

As explained above, according to the present invention, it is possible to achieve higher density than conventional VTRs in recording and reproducing PAL and SECAM color television signals.
Sufficient video signals can be obtained in both high-speed and reverse playback conditions, and even when the high-speed and reverse playback speeds are higher than in this example,
Very stable on screen.

[Brief explanation of drawings]

Figure 1 shows the recording trajectory of PAL and SECAM signal VTRs when αH = 1.5, and Figures 2, 3, and 4 show the recording trajectories for static, high-speed, and reverse playback when αH = 1.5, respectively. Figures 5, 6, and 7 are diagrams showing the playback locus; Figures 5, 6, and 7 are diagrams showing the order of video signal line numbers, color signals, and envelope waveforms corresponding to the playback of Figures 2, 3, and 4, respectively. , Figure 8 is
Figure 9 shows the basic signal processing block diagram of a VTR for VHS system PAL and SECAM signals.
A diagram showing the recording trajectory of a VTR for PAL and SECAM signals,
Figures 10, 11, and 12 are diagrams showing the playback trajectory in stationary, high-speed, and reverse playback when αH = 1.0.
Figures 11 and 12 show video signal line numbers, the order of color signals, and envelope waveforms corresponding to playback, and Figures 16 and 17 respectively show the VTR for PAL and SECAM signals according to the present invention. The basic block diagram of the signal processing circuit system, FIGS. 18 and 19, are respectively operational waveform diagrams of the control signal generation circuit in the correction circuit according to the present invention. 8...High-pass filter, 9...Low-pass filter, 1
0...Frequency demodulator, 11...Frequency converter, 1
2... Adder, 14... 1H delay circuit, 15...
Amplifier, 16... Envelope detector, 17...
Pulse generator, 18...integrator circuit, 19...inhibition circuit, 20...flip-flop, 21...changeover switch.

Claims (1)

[Claims] 1. Separate an input video signal using the PAL or SECAM system into a luminance signal and a carrier color signal, convert the luminance signal into an angle modulated wave, convert the carrier color signal to a low frequency, and generate the angle modulated signal. A diagonal track is formed on the recording medium using two heads having an azimuth angle to each other, and during reproduction, the angle modulated wave is demodulated to obtain a reproduced luminance signal, and the low frequency A video signal recording/reproducing device configured to convert the carrier color signal converted to the range frequency to the original frequency to obtain a reproduced carrier color signal, and to synthesize the reproduced luminance signal and the reproduced carrier color signal to obtain a reproduced video signal. In the device,
a first means for recording so that the starting ends of adjacent tracks on the recording medium are shifted by a distance corresponding to an integral multiple of one horizontal scanning period in the track extension direction, and outputting the reproduced transport color signal as is when reproducing;
a second means for outputting the output with a certain time delay, and a detecting means for detecting a different point in time of the color signal arrangement in the reproduced conveyed color signal in any one of a static, slow, high speed, and reverse reproduction state; and using the control signal obtained by the detection means, the output carrier color signals of the first and second means are alternately switched and extracted, and combined with the reproduced luminance signal to obtain a reproduced video signal. A video signal recording and reproducing apparatus characterized in that the delay time of the second means is set so that the color arrangement of the output conveyance color signals which are alternately switched and taken out is normal. 2. Claim 1, characterized in that the detection means for detecting different points in time in the color signal sequence in the reproduced carrier color signal generates a control signal by detecting an envelope of the reproduced carrier signal. 2. The video signal recording and reproducing device described in 2. 3. A control signal is generated by an output signal obtained from a deletion signal detector constituting a dropout compensation circuit as a detection means for detecting different points in time of color signal arrangement in a reproduced carrier color signal. A video signal recording and reproducing device according to claim 1.